An example of an illumination device for surface emission using a light guide plate is an edge light type illumination device 800 as shown in FIG. 18 (refer to Patent Document 1). FIG. 18 shows a plan view of the illumination device 800. In the illumination device 800, multiple light emitting elements 822 are annularly arranged around an outer periphery of a light guide plate 840 with their respective main emission directions directed to the light guide plate 840. Light emitted from the light emitting elements 822 enters the light guide plate 840 from an incident surface 840c which is an outer peripheral surface of the light guide plate 840, and is emitted uniformly from a light emitting surface 840a which is a front side surface of the light guide plate 840. A frame member 870 is attached to an outer periphery of the light guide plate 840 so as to cover the light emitting elements 822, whereby improvements in the protection of the light emitting elements 822 and the design of the illumination device 800 are achieved by the frame member 870.
However, if the frame member 870 is attached to the outer periphery of the light guide plate 840, the frame member 870 blocks light emitted from the outer periphery of the light guide plate 840, so that it is difficult to achieve emission from the entire surface on the front side of the illumination device 800.
Another example of an illumination device for surface emission using a light guide plate is a direct type illumination device 900 as shown in FIG. 19 (refer to Patent Document 2). FIG. 19 shows a cross-sectional view of the illumination device 900 while attached to a ceiling surface. In the illumination device 900, multiple light emitting elements 922 are annularly arranged on the back side of a light guide plate 940 with the main emission directions of the respective light emitting elements 922 directed to the light guide plate 940. Light emitted from the light emitting elements 922 enters an annular part 941 of the light guide plate 940 from an incident surface 944b formed on the back side of the annular part 941, and is reflected by a reflecting surface 941a as a front side surface of the annular part 941, and is further guided into an annular inner part 942 and an annular outer part 943 of the light guide plate 940. Then, this light is emitted uniformly from light emitting surfaces 942a, 943a which are front side surfaces of the annular inner part 942 and the annular outer part 943.
The arrangement of the light emitting elements 922 on the back side of the light guide plate 940, as in the illumination device 900, makes it unnecessary to attach a frame member to an outer periphery of the light guide plate 940, preventing the light emitted from the outer periphery of the light guide plate 940 from being blocked by the frame member, thus making it possible to achieve entire surface emission from the front side of the illumination device 900.